Hovering between 2 and 3. I can't help but think that what Kuttner considers a necessary social structure in the world he's constructed isn't actually optimistic. I'll give him the benefit of the doubt in that it is probably me who is overly pessimistic about humans.
For Mutant, in the end, Science wins over Fear, which might just be the most optimistic and least realistic part of the whole thing. That someday the right technology will instantly solve such complex and powerful human problems. Well, that or the part where everyone having easy access to atomic bombs results in generations of peace.